Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.46	7.629%	$238.3552	$238.36	$238.35	$238.40
Purchase #2	$131.25	10.789%	$145.4106	$145.41	$145.40	$145.40
Purchase #3	$150.55	9.545%	$164.92	$164.92	$164.90	$164.90
Purchase #4	$166.66	4.481%	$174.128	$174.13	$174.15	$174.10
Purchase #5	$52.68	7.619%	$56.6937	$56.69	$56.70	$56.70
Purchase #6	$235.60	9.471%	$257.9137	$257.91	$257.90	$257.90
Purchase #7	$100.99	4.869%	$105.9072	$105.91	$105.90	$105.90
7 purchase totals =	$1,059.19		$1,143.3284	$1,143.33	$1,143.30	$1,143.30